title: Nocturnal autonomic function in preschool children with sleep-disordered breathing.
abstract: BACKGROUND
  Obstructive sleep apnea (OSA) is associated with autonomic dysfunction in adults and school-aged children; however, this association has not been investigated in preschool children. We aimed to analyze heart rate variability (HRV) and catecholamine levels in preschool children with OSA.
  
  
  METHODS
  One hundred and forty-two snoring children aged 3-5years and 38 nonsnoring control group children underwent overnight polysomnography (PSG). Nocturnal urinary catecholamines were measured in 120 children. Children were grouped according to their obstructive apnea-hypopnea index (OAHI) (control [no snoring], OAHI⩽1event/h; primary snoring, OAHI⩽1event/h; mild OSA OAHI>1⩽5events/h; moderate to severe [MS] OSA, OAHI>5events/h). The HRV parameters for each child were averaged during rapid eye movement (REM) and non-REM (NREM) sleep.
  
  
  RESULTS
  During stable sleep, low-frequency (LF) HRV was similar between groups. High-frequency (HF) HRV was higher in the MS OSA group compared with the control group during all sleep stages (NREM sleep stages 1 and 2 [NREM1/2], 4234±523ms(2) vs 2604±457ms(2); NREM sleep stages 3 and 4 [NREM3/4], 4152±741ms(2) vs 3035±647ms(2); REM, 1836±255ms(2) vs 1456±292ms(2); P<.01 for all). The LF/HF ratio was lower in the MS OSA group compared with the control group (NREM1/2, 0.4±0.06 vs 0.7±0.05; NREM3/4, 0.3±0.06 vs 0.4±0.05; REM, 0.8±0.1 vs 1.3±0.1; P<.01 for all). Catecholamine levels were not different between groups.
  
  
  CONCLUSIONS
  In preschool children, OSA is associated with altered HRV, largely due to the HF fluctuations in heart rate (HR) which occur during respiratory events and are still evident during stable sleep. The preschool age may represent a window of opportunity for treatment of OSA before the onset of the severe autonomic dysfunction associated with OSA in adults and older children.
authors.affiliation: The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Australia.
authors.forename: Lauren C
authors.initials: LC
authors.lastname: Nisbet
authors.forename: Stephanie R
authors.initials: SR
authors.lastname: Yiallourou
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Nixon
authors.forename: Sarah N
authors.initials: SN
authors.lastname: Biggs
authors.forename: Margot J
authors.initials: MJ
authors.lastname: Davey
authors.forename: John
authors.initials: J
authors.lastname: Trinder
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Walter
authors.forename: Rosemary S C
authors.initials: RS
authors.lastname: Horne
mesh_terms: D001341:Autonomic Nervous System / Q000502:physiology*; D002675:Child, Preschool; D004298:Dopamine / Q000652:urine; D004837:Epinephrine / Q000652:urine; D005260:Female; D006321:Heart / Q000502:physiology*; D006801:Humans; D008297:Male; D010625:Phenylethanolamine N-Methyltransferase / Q000652:urine; D012891:Sleep Apnea Syndromes / Q000503:physiopathology*; D012894:Sleep Stages / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology*; D012913:Snoring / Q000503:physiopathology
chemical_list: D010625:Phenylethanolamine N-Methyltransferase; D004298:Dopamine; D004837:Epinephrine
keywords: Autonomic nervous system; Catecholamines; Heart rate; Heart rate variability; Pediatric; Sleep disordered breathing